Northside Health Library

Glucose-6-phosphate dehydrogenase

Definition

Glucose-6-phosphate dehydrogenase (G6PD) is a type of protein, called an enzyme, that helps red blood cells work properly. The G6PD test looks at the amount (activity) of this substance in a patient's red blood cells.

Alternative Names

RBC G6PD test; G6PD screen

How the Test is Performed

A blood sample is needed. For information on how this is done, see: Venipuncture

How to Prepare for the Test

No special preparation is usually necessary.

How the Test Will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the Test is Performed

Your doctor may order this test if you have signs of G6PD deficiency. This means you do not have enough G6PD activity.

Too little G6PD activity leads to the destruction of red blood cells. This process is called hemolysis. When this process is actively occurring, it is called a hemolytic episode.

If this test is done during a hemolytic episode it may be falsely positive and misleading. This is because the cells most likely to have low G6PD levels (older cells) have been destroyed, and those remaining may show normal G6PD levels.

After recovery from the episode, older cells will show lower levels of G6PD, resulting in a positive test.

Normal Results

Normal values vary and depend upon the laboratory used. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results mean you have a G6PD deficiency, which can cause hemolytic anemia in certain conditions.

Risks

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include: